Technical Foundation
What Is a Deadlatch Hardware?
A deadlatch is a spring-loaded latch bolt fitted with a secondary anti-shim plunger that deadlocks the bolt once the door closes, preventing the latch from being retracted by inserting a shim or credit card between the bolt and the strike. This makes deadlatch hardware the standard auxiliary lock on commercial storefront and entry doors, typically paired with a mortise lock body or installed as a stand-alone rim or mortise auxiliary latch.
Deadlatch hardware is specified by backset (the distance from the door edge to the center of the strike or cylinder), latch throw (how far the bolt projects, commonly 1/2 inch to 1 inch), and door prep — narrow stile aluminum doors need a compact case that fits a 1-3/4 to 2 inch stile width, while wood or hollow-metal commercial doors use a standard mortise pocket. ANSI/BHMA A156.5 grades deadlatch cylinders and hardware for security and cycle-life performance.
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| Spec | What It Means | Why It Matters |
|---|---|---|
| Backset | Distance from door edge to strike/cylinder centerline, commonly 2-3/4 in. or 3-5/8 in. | Must match the door prep exactly or the strike and latch will not align |
| Latch Throw | Bolt projection, typically 1/2 in. to 1 in. | Longer throw resists spreading attacks on the door frame gap |
| ANSI/BHMA A156.5 Grade | Grade 1, 2, or 3 cylinder and latch performance rating | Grade 1 is specified for high-traffic commercial and high-security entrances |
| Anti-Shim Plunger | Secondary deadlocking pin activated when the door closes | Prevents latch bolt retraction by shim, card, or loid attack |
| Door Prep | Narrow stile, mortise, or rim-mount case dimensions | A narrow stile aluminum door cannot accept a standard mortise case |
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Applications
Where Deadlatch Hardware Get Used
Deadlatch hardware is specified anywhere a door needs shim-resistant latching in addition to, or instead of, a standalone deadbolt.
Commercial Storefront Entrances
Narrow stile aluminum door deadlatches paired with panic exit devices on retail and office storefronts.
Multi-Tenant Office Buildings
Grade 1 auxiliary deadlatches on mortise lock bodies specified for high-cycle common entry doors.
Educational Facilities
Deadlatch hardware combined with classroom function locksets to meet school security hardware schedules.
Healthcare Facilities
Anti-shim deadlatch bolts on stairwell and corridor doors as part of a fire/life-safety door hardware set.
Residential Entry Doors
Auxiliary deadlatches installed above a primary deadbolt for added forced-entry resistance.
Government & Institutional Buildings
High-security Grade 1 deadlatch cylinders specified under GSA and ANSI hardware standards.
FAQ
Deadlatch Hardware Questions, Answered
What makes a deadlatch different from a standard spring latch?
A standard spring latch bolt has a beveled face that can be retracted by inserting a thin shim or card between the bolt and the strike plate. A deadlatch adds a secondary plunger next to the latch bolt that gets depressed when the door closes fully into the strike, mechanically locking the latch bolt in place so it can't be shimmed back — the door has to be unlocked with a key or lever to open it.
How do I determine the correct backset for a deadlatch?
Backset is measured from the edge of the door to the center of the bore hole or strike, and it must match the existing door prep exactly — common sizes are 2-3/4 inch and 3-5/8 inch for commercial applications. Measuring an existing installation, or checking the door hardware schedule/architectural spec for narrow stile and mortise preps, avoids ordering a deadlatch that won't fit the existing bore.
What ANSI/BHMA grade should I specify for a commercial entrance?
ANSI/BHMA A156.5 Grade 1 is typically specified for main commercial entrances and high-traffic doors because it's rated for the highest cycle life and security performance. Grade 2 is common for secondary or interior commercial doors, while Grade 3 covers lighter-duty residential and light-commercial use.
Can a deadlatch be used on a narrow stile aluminum storefront door?
Yes — narrow stile deadlatches are built into a compact case sized to fit inside a 1-3/4 to 2 inch aluminum door stile, which is too narrow for a standard mortise lock body. These are commonly paired with panic exit hardware or a narrow stile lock trim on storefront and office entrance doors.
Does a deadlatch replace the need for a separate deadbolt?
Not necessarily — many commercial doors use a deadlatch as the primary latching hardware because its anti-shim feature already provides forced-entry resistance, but higher-security applications often add a separate deadbolt above it for redundant throw-bolt security. The hardware schedule or the door's UL/fire rating typically dictates which combination is required.
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